.back {
  position: absolute;
  left: 0.5rem;
  top: 0.5rem;
  background-color: aliceblue;
}

.back i {
  color: #3f51b5;
}

.tips {
  color: #666;
  text-align: center;
  font-size: 14px;
  width: 10rem;
  position: absolute;
  top: 2rem;
  left: 1rem;
  right: 1rem;
}

.codes {
  position: absolute;
  top: 4rem;
  left: 1rem;
  right: 1rem;
  width: 10rem;
  display: flex;
}

.code {
  color: #666;
  font-size: 16px;
  text-align: center;
  flex: 1;
  width: 1rem;
  height: 1rem;
  line-height: 1rem;
  margin: 0 0.1rem;
  outline: none;
  border: none;
  border-bottom: 1px solid #3f51b5;
}

.mat-raised-button {
  width: 6rem;
  color: #3f51b5;
  background-color: rgba(63, 81, 181, .2);
}

.confirm {
  text-align: center;
  font-size: 16px;
  position: absolute;
  top: 6rem;
  left: 3rem;
  right: 3rem;
}
